From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [PATCH v4 1/7] s390: ap: kvm: add PQAP interception for AQIC Date: Thu, 28 Feb 2019 10:36:09 -0500 Message-ID: <0051da1a-1834-8bb0-b277-ae434cb7d755@linux.ibm.com> References: <1550849400-27152-1-git-send-email-pmorel@linux.ibm.com> <1550849400-27152-2-git-send-email-pmorel@linux.ibm.com> <9f1d9241-39b9-adbc-d0e9-cb702e609cbc@linux.ibm.com> <4dc59125-7f96-cba8-651b-382ed8f8bff8@linux.ibm.com> <8526f468-9a4d-68d2-3868-0dad5ce16f46@linux.ibm.com> <6058a017-6404-af3c-62ef-2452214ac97c@de.ibm.com> <2391adc2-6611-034c-61c5-feb46e2a751b@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2391adc2-6611-034c-61c5-feb46e2a751b@de.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Christian Borntraeger , pmorel@linux.ibm.com Cc: alex.williamson@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com List-ID: On 2/28/19 6:03 AM, Christian Borntraeger wrote: > > > On 28.02.2019 10:42, Christian Borntraeger wrote: > [...] >>> Okay, let's go back to the genesis of this discussion; namely, my >>> suggestion about moving the fc == 0x03 check into the hook code. If >>> the vfio_ap module is not loaded, there will be no hook code. In that >>> case, the check for the hook will fail and ultimately response code >>> 0x01 will be set in the status word (which may not be the right thing >>> to do?). You have not stated a single good reason for keeping this >>> check, but I'm done with this silly argument. It certainly doesn't >>> hurt anything. >> >> The instruction handler must handle the basic checks for the >> instruction itself as outlined above. >> >> Do we want to allow QEMU to fully emulate everything (the ECA_APIE case being off)? >> The we should pass along everything to QEMU, but this is already done with the >> ECA_APIE check, correct? >> >> Do we agree that when we are beyond the ECA_APIE check, that we do not emulate >> in QEMU and we have enabled the AP instructions interpretion? >> If yes then this has some implication: >> >> 1. ECA is on and we should only get PQAP interception for specific FC (namely 3). >> 2. What we certainly should check is the facility bit of the guest (65) and reject fc==3 >> right away with a specification exception. I do not want the hook to mess with >> the kvm cpu model. @Pierre would be good to actually check test_kvm_facility(vcpu->kvm, 65)) >> 3. What shall we do when fc == 0x3? We can certainly do the check here OR in the >> hook. As long as we have only fc==3 this does not matter. >> >> Correct? > > Thinking more about that, I think we should inject a specification exception for all > unknown FCc != 0x3. That would also qualify for keeping it in the instruction handler. Sure, let's do it. >